Fernández Escobar, Mercedes

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First Name
Last Name
Fernández Escobar
Universidad Complutense de Madrid
Faculty / Institute
Sanidad Animal
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Now showing 1 - 7 of 7
  • Publication
    Toxoplasma gondii Genetic Diversity in Mediterranean Dolphins
    (MPDI, 2022-08-12) Fernández Escobar, Mercedes; Giorda, Federica; Mattioda, Virgina; Audino, Tania; Di Nocera, Fabio; Lucifora, Giuseppe; Varello, Katia; Grattarola, Carla; Ortega Mora, Luis Miguel; Casalone, Cristina; Calero Bernal, Rafael
    Toxoplasma gondii constitutes a major zoonotic agent but also has been frequently identified as an important cause of clinical disease (e.g., abortion, pneumonia, encephalitis) in wildlife; specifically, T. gondii has been associated with neurological disease in cetaceans. This study investigated the genetic diversity of T. gondii strains involved in infections in dolphins found stranded in the Mediterranean coastlines of Italy. Tissue samples from 16 dolphins (Stenella coeruleoalba and Tursiops truncatus species) positive for T. gondii-DNA presence by PCR were examined by histology and subjected to further genetic characterization of strains detected by PCR-RFLP and multilocus PCR-sequencing assays. According to fully genotyped samples, the genotypes ToxoDB#3 (67%) and #2 (22%) were detected, the latter being reported for the first time in cetaceans, along with a mixed infection (11%). Subtyping by PCR-seq procedures provided evidence of common point mutations in strains from southwestern Europe. Despite evidence of T. gondii as a cause of neurological disease in dolphins, sources of infections are difficult to identify since they are long-living animals and some species have vast migration areas with multiple chances of infection. Finally, the genetic diversity of T. gondii found in the dolphins studied in the Mediterranean coastlines of Italy reflects the main genotypes circulating inland in the European continent.
  • Publication
    Effects of Ovine Monocyte-Derived Macrophage Infection by Recently Isolated Toxoplasma gondii Strains Showing Different Phenotypic Traits
    (MPDI, 2022-12-07) Vallejo, Raquel; Benavides, Julio; Arteche Villasol, Noive; Fernández Escobar, Mercedes; Ferreras, María Del Carmen; Pérez, Valentín; Gutierrez Expósito, Daniel
    Ovine toxoplasmosis is one the most relevant reproductive diseases in sheep. The genetic variability among different Toxoplasma gondii isolates is known to be related to different degrees of virulence in mice and humans, but little is known regarding its potential effects in sheep. The aim of this study was to investigate the effect of genetic variability (types II (ToxoDB #1 and #3) and III (#2)) of six recently isolated strains that showed different phenotypic traits both in a normalized mouse model and in ovine trophoblasts, in ovine monocyte-derived macrophages and the subsequent transcript expression of cytokines and iNOS (inducible nitric oxide synthase). The type III isolate (TgShSp24) showed the highest rate of internalization, followed by the type II clonal isolate (TgShSp2), while the type II PRU isolates (TgShSp1, TgShSp3, TgShSp11 and TgShSp16) showed the lowest rates. The type II PRU strains, isolated from abortions, exhibited higher levels of anti-inflammatory cytokines and iNOS than those obtained from the myocardium of chronically infected sheep (type II PRU strains and type III), which had higher levels of pro-inflammatory cytokines. The present results show the existence of significant intra- and inter-genotypic differences in the parasite-macrophage relationship that need to be confirmed in in vivo experiments.
  • Publication
    Evidence for Unknown Sarcocystis-Like Infection in Stranded Striped Dolphins (Stenella coeruleoalba) from the Ligurian Sea, Italy
    (MPDI, 2021-04-22) Giorda, Federica; Romani Cremaschi, Umberto; Marsh, Antoinette E.; Grattarola, Carla; Iulini, Barbara; Pautasso, Alessandra; Varello, Katia; Berio, Enrica; Gazzuola, Paola; Marsili, Letizia; Di Francesco, Cristina E.; Goria, Maria; Verna, Federica; Audino, Tania; Peletto, Simone; Caramelli, Maria; Fernández Escobar, Mercedes; Sierra, Eva; Fernández, Antonio; Calero Bernal, Rafael; Casalone, Cristina
    Two striped dolphins (SD1, SD2), stranded along the Ligurian coast of Italy, were diagnosed with a nonsuppurative meningoencephalitis associated with previously undescribed protozoan tissue cysts. As tissue cysts were morphologically different from those of Toxoplasma gondii, additional histopathological, immunohistochemical, ultrastructural, and biomolecular investigations were performed, aiming to fully characterize the organism. Histopathology revealed the presence of large Sarcocystis-like tissue cysts, associated with limited inflammatory lesions in all CNS areas studied. IHC was inconclusive, as positive staining with polyclonal antisera did not preclude cross-reaction with other Sarcocystidae coccidia. Applied to each animal, 11 different PCR protocols precluded a neural infection by Sarcocystis neurona, Sarcocystis falcatula, Hammondia hammondi, and Neospora caninum. T. gondii coinfection was confirmed only in dolphin SD2. Sarcocystis sp. sequences, showing the highest homology to species infecting the Bovidae family, were amplified from SD1 myocardium and SD2 skeletal muscle. The present study represents the first report of Sarcocystis-like tissue cysts in the brain of stranded cetaceans along with the first description of Sarcocystis sp. infection in muscle tissue of dolphins from the Mediterranean basin.
  • Publication
    Genetic and phenotypic characterization of Toxoplasma gondii isolates obtained from sheep and Iberian pigs in Spain
    (Universidad Complutense de Madrid, 2022-02-17) Fernández Escobar, Mercedes; Ortega Mora, Luis Miguel; Collantes Fernández, Esther; Calero Bernal, Rafael
    Toxoplasma gondii is an apicomplexan parasite globally distributed with a heteroxenous life cycle that virtually comprises all homoeothermic animals, including humans, as intermediate hosts and felids as definitive hosts. The zoonotic, abortifacient, and foodborne nature of the parasite makes toxoplasmosis a relevant public and animal health concern worldwide.A comprehensive research effort on T. gondii biology along with the rapid development of molecular techniques suitable for strains genotyping over the last decades, led to the initial description of a widely clonal European and North American T. gondii genetic population dominated by three main clonal genetic types (I, II, and III), in contrast to an extremely diverse South American population. However, the information available from Europe is limited, with frequent methodological deficiencies and important sampling disparities among regions. Briefly, the available European literature evidences a clear predominance of type II strains (comprising around 80% of samples) coexisting with much less abundant type III and recombinant strains or mixed infections, as well as minor proportions of type I and imported genotypes. In the specific case of Spain, the majority of the scarce investigations dealt with direct genotyping from clinical samples, with the subsequent limitations to classify the strains and the impossibility of extending its characterization...
  • Publication
    Dynamics of Neospora caninum-Associated Abortions in a Dairy Sheep Flock and Results of a Test-and-Cull Control Programme
    (MPDI, 2021-11-20) Sánchez Sánchez, Roberto; Vázquez Calvo, Ángela; Fernández Escobar, Mercedes; Regidor Cerrillo, Javier; Benavides, Julio; Gutiérrez, Jorge; Gutierrez Expósito, Daniel; Crespo Ramos, Francisco José; Ortega Mora, Luis Miguel; Álvarez García, Gema
    Neospora caninum is an apicomplexan parasite that can cause abortions and perinatal mortality in sheep. Although ovine neosporosis has been described worldwide, there is a lack of information about the relationship between N. caninum serostatus and the reproductive performance. In this study, we described the infection dynamics in a dairy sheep flock with an abortion rate up to 25% and a N. caninum seroprevalence of 32%. Abortions were recorded in 36% and 9% of seropositive and seronegative sheep, respectively. Seropositive sheep were more likely to abort twice (OR = 4.44) or three or more times (OR = 10.13) than seronegative sheep. Endogenous transplacental transmission was the main route of transmission since 86% of seropositive sheep had seropositive offspring. Within dams that had any abortion, seropositive sheep were more likely than seronegative ones to have female descendants that aborted (OR = 8.12). The slight increase in seropositivity with the age, the low percentage of animals with postnatal seroconversion or with low avidity antibodies, and the seropositivity of one flock dog, indicated that horizontal transmission might have some relevance in this flock. A control programme based on selective culling of seropositive sheep and replacement with seronegative animals was effective in reducing the abortion rate to 7.2%.
  • Publication
    Isolation and genetic characterization of Toxoplasma gondii in Spanish sheep flocks
    (2020-08-05) Julio Benavides; Fernández Escobar, Mercedes; Calero Bernal, Rafael; Javier Regidor-Cerrillo; María Cristina Guerrero-Molina; Daniel Gutiérrez-Expósito; Collantes Fernández, Esther; Ortega Mora, Luis Miguel
    Background: Toxoplasma gondii is a major cause of abortion in small ruminants and presents a zoonotic risk when undercooked meat containing cysts is consumed. The aim of the present study was to investigate the genetic diversity among the T. gondii strains circulating in ovine livestock in Spain. Methods: Selected samples collected from abortion outbreaks due to toxoplasmosis (n = 31) and from chronically infected adult sheep at slaughterhouses (n = 50) in different Spanish regions were bioassayed in mice, aiming at parasite isolation. In addition, all original clinical samples and the resulting isolates were genotyped by multi-nested PCR-RFLP analysis of 11 molecular markers and by PCR-DNA sequencing of portions of the SAG3, GRA6 and GRA7 genes. Results: As a result, 30 isolates were obtained from 9 Spanish regions: 10 isolates from abortion-derived samples and 20 isolates from adult myocardial tissues. Overall, 3 genotypes were found: ToxoDB#3 (type II PRU variant) in 90% (27/30) of isolates, ToxoDB#2 (clonal type III) in 6.7% (2/30), and ToxoDB#1 (clonal type II) in 3.3% (1/30). When T. gondii-positive tissue samples (n = 151) were directly subjected to RFLP genotyping, complete restriction profiles were obtained for 33% of samples, and up to 98% of the specimens belonged to the type II PRU variant. A foetal brain showed a clonal type II pattern, and four specimens showed unexpected type I alleles at the SAG3 marker, including two foetal brains that showed I + II alleles as co-infection events. Amplicons of SAG3, GRA6 and GRA7 obtained from isolates and clinical samples were subjected to sequencing, allowing us to confirm RFLP results and to detect different single-nucleotide polymorphisms. Conclusions: The present study informed the existence of a predominant type II PRU variant genotype (ToxoDB#3) infecting domestic sheep in Spain, in both abortion cases and chronic infections in adults, coexisting with other clonal (ToxoDB#1 and ToxoDB#2), much less frequent genotypes, as well as polymorphic strains as revealed by clinical sample genotyping. The use of multilocus sequence typing aided in accurately estimating T. gondii intragenotype diversity.
  • Publication
    In vivo and in vitro models show unexpected degrees of virulence among Toxoplasma gondii type II and III isolates from sheep
    (BMC, 2021-06-10) Fernández Escobar, Mercedes; Ortega Mora, Luis Miguel; Collantes Fernández, Esther; Calero Bernal, Rafael; Regidor-Cerrillo, Javier; Vallejo, Raquel; Benavides, Julio
    Toxoplasma gondii is an important zoonotic agent with high genetic diversity, complex epidemiology, and variable clinical outcomes in animals and humans. In veterinary medicine, this apicomplexan parasite is considered one of the main infectious agents responsible for reproductive failure in small ruminants worldwide. The aim of this study was to phenotypically characterize 10 Spanish T. gondii isolates recently obtained from sheep in a normalized mouse model and in an ovine trophoblast cell line (AH-1) as infection target cells. The panel of isolates met selection criteria regarding such parameters as genetic diversity [types II (ToxoDB #1 and #3) and III (#2)], geographical location, and sample of origin (aborted foetal brain tissues or adult sheep myocardium). Evaluations of in vivo mortality, morbidity, parasite burden and histopathology were performed. Important variations between isolates were observed, although all isolates were classified as “nonvirulent” (< 30% cumulative mortality). The isolates TgShSp16 (#3) and TgShSp24 (#2) presented higher degrees of virulence. Significant differences were found in terms of in vitro invasion rates and tachyzoite yield at 72 h post-inoculation (hpi) between TgShSp1 and TgShSp24 isolates, which exhibited the lowest and highest rates, respectively. The study of the CS3, ROP18 and ROP5 loci allelic profiles revealed only type III alleles in ToxoDB #2 isolates and type II alleles in the #1 and #3 isolates included. We concluded that there are relevant intra- and inter-genotype virulence differences in Spanish T. gondii isolates, which could not be inferred by genetic characterization using currently described molecular markers.